Together with other inhabitants of Tuonela, the Son of Tuoni (Tuonen poika) weaves an iron net and sets it across the River of Tuonela to prevent the mage Väinämöinen from escaping the land of the dead.
Mana’s son with crooked fingers,
Iron-pointed, copper fingers,
Pulls of nets, at least a thousand,
Through the river of Tuoni,
Sets them lengthwise,
sets them crosswise,
In the fatal, darksome river,
That the sleeping Wainamomen,
Friend and brother of the waters,
May not leave the isle of Mana.
In the morning, the Boy checks his nets, but during the night, the old mage has transformed into a snake and swum through the nets back into the world of the living.
In the Finnish national epic Kalevala, the author Elias Lönnrot has given the Son of Tuoni an additional role that cannot be found in ancient poems: he kills a warrior-wizard Lemminkäinen with his sword and leaves his body pieces floating in the river of the dead.
There the blood-stained son of death-land,
There Tuoni’s son and hero,
Cuts in pieces Lemminkainen,
Chops him with his mighty hatchet,
Till the sharpened axe strikes flint-sparks
From the rocks within his chamber,
Chops the hero into fragments,
Into five unequal portions,
Throws each portion to Tuoni,
In Manala’s lowest kingdom.